The present invention relates generally to inkjet printers, and more particularly to an inkjet printer including a carriage drive belt having a compliant belt section which provides varying tension with displacement.
A conventional inkjet printing system includes a printhead assembly, an ink supply which supplies liquid ink to the printhead assembly, and an electronic controller which controls the printhead assembly. The printhead assembly, commonly referred to as a print carriage or a pen, ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a piece of paper, to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead assembly and the print medium are moved relative to each other.
To position the printhead assembly relative to the print medium, the conventional inkjet print system includes a carriage assembly. Typically, the carriage assembly includes a carriage and a carriage drive assembly. As such, the printhead assembly is positioned in, and supported by, the carriage and the carriage drive assembly moves the carriage and, therefore, the printhead assembly back and for the across the print medium.
As illustrated in FIG. 1, a conventional carriage drive assembly 200 typically includes a drive pulley 202, a drive belt 204, an idler pulley 206, and a belt tension spring 208. The idler pulley is spaced from the drive pulley, and the drive belt extends between and around the drive pulley and the idler pulley. The drive pulley is attached to a drive motor (not shown) by a drive shaft 210 to transfer power to the drive pulley and the drive belt. Power transfer from the drive pulley to the drive belt moves a section of the drive belt back and forth between the drive pulley and the idler pulley. Typically, the drive pulley and/or the idler pulley has a reciprocal toothed contour designed to mate with the toothed contour of the drive belt. A carriage 212 (only a portion of which is illustrated in FIG. 1) is attached to the drive belt such that the carriage moves with the drive belt between the drive pulley and the idler pulley.
The belt tension spring and the idler pulley interact such that the belt tension spring pushes or biases the idler pulley away from the drive pulley to provide a pre-load tension in the drive belt. This pre-load tension provides a static axial force or nominal tension in the drive belt before and during acceleration of the carriage from rest. As such, the pre-load tension maintains sufficient contact between the drive belt and the drive pulley. By maintaining proper contact between the drive belt and the drive pulley, power is more efficiently transmitted from the drive pulley to the drive belt. The belt tension spring also functions to temper vibration caused by interaction of the drive belt and the drive pulley as well as compensate for manufacturing variations and/or environmental conditions such as temperature or humidity.
Interaction between the belt tension spring and the idler pulley requires that the idler pulley vary its position in response to force applied by the belt tension spring. Thus, the carriage drive assembly must include an adjustable or moveable idler pulley. Unfortunately, providing the carriage drive assembly with a moveable idler pulley adds to the manufacturing complexity and cost of the carriage drive assembly since additional components and manufacturing steps are required compared with a fixed pulley design.
One arrangement for providing a pre-load tension in a drive belt was included in the ScanJet 6300C/Cse/Cxi series scanners produced by Hewlett-Packard Company of Palo Alto, Calif., the present assignee. This arrangement included a coil spring wound in a direction perpendicular to a length of the drive belt with projecting arms at opposite ends which were hooked over the drive belt. This arrangement, however, is unsuitable for drive systems requiring high acceleration, such as an inkjet printing system, because the arms will deflect before the coil spring windings thereby reducing a desired pre-load tension in the drive belt and resulting in slip between the drive belt and the drive motor pulley.
Accordingly, a need exists for a belt tensioning arrangement for a carriage drive assembly of an inkjet printer which reduces manufacturing complexity and cost by operating between fixed drive and idler pulleys.
One aspect of the present invention provides a carriage drive belt for an inkjet printer. The carriage drive belt includes an elongated belt section and a compliant belt section secured to the elongated belt section. The elongated belt section has a longitudinal axis and includes a first portion and a second portion spaced from the first portion along the longitudinal axis. The compliant belt section extends between the first portion and the second portion of the elongated belt section and has an axis extending in a direction of the longitudinal axis of the elongated belt section.
Another aspect of the present invention provides a method of forming a carriage drive belt for an inkjet printer. The method includes providing an elongated belt section having a longitudinal axis and including a first portion and a second portion spaced from the first portion along the longitudinal axis, extending a compliant belt section having an axis and including a first end and a second end between the first portion and the second portion of the elongated belt section, and securing the compliant belt section to the elongated belt section. Extending the compliant belt section between the first portion and the second portion of the elongated belt section includes extending the axis of the compliant belt section in a direction of the longitudinal axis of the elongated belt section. Securing the compliant belt section to the elongated belt section includes securing the first end of the compliant belt section to the first portion of the elongated belt section and securing the second end of the compliant belt section to the second portion of the elongated belt section.
Another aspect of the present invention provides an inkjet printer. The inkjet printer includes a first pulley and a second pulley, and a carriage drive belt. The second pulley is spaced a fixed distance from the first pulley and the carriage drive belt extends around and between the first pulley and the second pulley. The carriage drive belt includes an elongated belt section and a compliant belt section. The elongated belt section has a longitudinal axis and includes a first portion and a second portion spaced from the first portion along the longitudinal axis. The compliant belt section extends between and is secured to the first portion and the second portion of the elongated belt section such that an axis of the compliant belt section extends in a direction of the longitudinal axis of the elongated belt section.